Non-dystrophic myotonia Chilean cohort with predominance of the SCN4A Gly1306Glu variant.

Abstract

Non-dystrophic myotonias are a group of rare neuromuscular diseases linked to SCN4A or CLCN1. Among the subtypes, myotonia permanens, associated with the Gly1306Glu variant of SCN4A, is a relatively less frequent but more severe form. Most reports of non-dystrophic myotonias describe European populations. Therefore, to expand the genetic and phenotypic spectrum of this disorder, we evaluated 30 Chilean patients with non-dystrophic myotonias for associated variants and clinical characteristics. SCN4A variants were observed in 28 (93%) of patients, including 25 (83%) with myotonia permanens due to the Gly1306Glu variant. Myotonia permanens was inherited in 24 (96%) patients; the mean age of onset was 6 months, and the initial symptoms were orbicularis oculi myotonia in 17 (74%) patients and larynx myotonia in 12 (52%) patients. The extraocular muscles were involved in 11 (44%) patients, upper limbs in 20 (80%), and lower limbs in 21 (84%). Thirteen (52%) patients experienced recurrent pain and 10 (40%) patients reported limitations in daily life activities. Carbamazepine reduced myotonia in eight treated patients. The high frequency of the Gly1306Glu variant in SCN4A in Chilean patients suggests a founder effect and expands its phenotypic spectrum.

• Authors: Daniela Avila-Smirnow, Carmen Paz Vargas Leal, María de Los Angeles Beytía Reyes, Rocío Cortés Zepeda, Raúl G Escobar, Karin Kleinsteuber Saa, Marcela Lagos Lucero, María de Los Angeles Avaria Benapres, Oslando Padilla Pérez, Juan Carlos Casar Leturia, Cecilia Mellado Sagredo, Damien Sternberg
• Journal: Neuromuscular disorders : NMD (Neuromuscul Disord) Vol. 30 Issue 7 Pg. 554-561 (07 2020) ISSN: 1873-2364 [Electronic] England
• PMID: 32593548 (Publication Type: Journal Article)
• Copyright: Copyright © 2020 Elsevier B.V. All rights reserved.

Chemical References

• NAV1.4 Voltage-Gated Sodium Channel
• SCN4A protein, human

Topics

• Adolescent
• Adult
• Child
• Chile
• Cohort Studies
• Female
• Founder Effect
• Humans
• Infant
• Male
• Mutation
• Myotonia (genetics)
• Myotonic Disorders (genetics)
• NAV1.4 Voltage-Gated Sodium Channel (genetics)
• Young Adult